Write a short letter filled with as many details about your neighbors as possible. "I've seen the Jablonski boy harming animals, and I'm convinced he'll be a serial killer some day. The lady across the avenue with the big hair who is always watching TV seems to never leave the house. Mr. Doymiller methodically mows his lawn every three days, whether it's raining or not."

That kind of stuff could be gold.

I totally agree with the funny neighborhood observations.  Also, some articles about the current state of our economy, for perspective...just 'cause I feel like all of our current economic news, while very bad, has been blown out of proportion in the day-to-day reporting.

current magazine such as Atlantic or Harpers, old and unused cell phone, anything disposable you consider "modern", a grocery store flyer showing current prices, a shirt, shoes, ear-bud headphones, bottle of wine or whiskey, electric bill, a computer mouse, an incandescent light bulb, a receipt from Target, Walgreens or Wal Mart...pretty much anything, really.

shower curtain rings. you never know if they'll have those in the future.

A lot of time when I look at old pictures I find myself interested in a background detail of where it was taken and what things were like at that moment in time.  

So, how about some pictures from around the neighborhood?  Wide shots that get in stuff like the way houses are painted, landscaping, cars in front of them, kids playing stuff and fashions, popular stores, etc.  Potholes.  And while you're at it, why not do your own house? So you or whomever can see how the furniture was arranged, painted, cabinets, cleanliness vs. dissarray and all of that.

ooh..ooh.. add detailed care and feeding instructions for the "pet". And a pic, if you can of an appropriate animal with a pet name scrawled on it..

I'm going to try that link again.

a rusted .38 special with a spent cartridge in the chamber, A one-eyed-jack bicycle playing card and some tapioca ... but that's just me

Any print articles making predictions about the future.
Articles about Obama breaking race barriers.
Articles about global warming.
Articles predicting the end of the world in 2012.
A treasure map.
A small Tim Kaiser instrument.
A Hammacher Shlemmer catalogue.
Pictures of enormous SUVs
A vial of clean water.
A love-letter.
An I.O.U.

USB keychains are cheap now. You could load one up with your favorite music and a bunch of photos. It'll end up being some nerd's delight to reverse engineer a USB device to fit into the holo-projector.

Burnt CDs / DVDs aren't considered archival.